1. Field of the Invention
This invention relates to a magnetic disc cartridge which contains a magnetic disc medium having a storage capacity different from those of conventional magnetic disc cartridges and is provided with one or more holes for distinguishing the magnetic disc cartridge from other magnetic disc cartridges.
2. Description of the Related Art
There has been known a magnetic disc medium, a so-called floppy disc, which comprises magnetic layers formed on opposite sides of a flexible disc base of a polyester sheet or the like. Information is recorded on the floppy disc by a magnetic head while rotating the floppy disc. The floppy disc is generally contained in a thin casing and is used in the form of a magnetic disc cartridge. Such magnetic disc cartridges have been mainly used as recording media for computers because they are easy to handle and can be produced at low cost.
Recently the storage capacity of the magnetic disc medium of the magnetic disc cartridge has been increased by change in the recording system, improvement of the magnetic layer and the like. When a magnetic disc cartridge having a larger storage capacity is provided and introduced into the market, it is necessary for the larger capacity magnetic disc cartridge to be provided with a function of distinguishing itself from the magnetic disc cartridges having the conventional standard storage capacity (e.g., 3.5-inch floppy disc cartridge having a storage capacity of 1 MB to 2 MB).
As a means for distinguishing magnetic disc cartridges of different storage capacities from each other, there has been known a system involving one or more through or blind holes formed in the casing to be detectable mechanically or optically. For example, in the case of 3.5-inch magnetic disc cartridges, a distinguishing hole for distinguishing those of 2 MB from others is formed in a rear corner of the casing (one of the corners on the edge of the casing remote from the shutter). In the case of magnetic disc cartridges of 10 MB and 21 MB, such a distinguishing hole is formed adjacent to the shutter.
In the case of novel magnetic disc cartridges of a large storage capacity such as of 100 MB or more, the vicinity of the space where the distinguishing hole for 10 MB or 21 MB is to be formed is too narrow to form a distinguishing hole for the large storage capacity and accordingly it is preferred that the distinguishing hole for the large storage capacity be formed on a rear (as seen in the direction of insertion of the magnetic disc cartridge) edge portion of the casing remote from the shutter.
Further in order to prevent accidental erasure of recorded information on the novel magnetic disc cartridge when the novel magnetic disc cartridge is loaded in a disc drive system for conventional magnetic disc cartridges, a first distinguishing hole is formed in the part corresponding to the part of the conventional magnetic disc cartridge (e.g., of 2 MB) where a write protector is provided, and the first distinguishing hole functions as a distinguishing hole representing a reference storage capacity different from the storage capacity of the conventional magnetic disc cartridges.
In view of assembly of disc drive systems and the manufacturing cost, it is advantageous that sensors for detecting the distinguishing holes of the magnetic disc cartridge are collectively provided in the disc drive systems.
Further a disc drive system is generally provided with a medium sensor which extends in parallel or perpendicular to the direction of insertion of a magnetic disc cartridge near the write protector or the first distinguishing hole and the disc drive system detects that a magnetic disc cartridge is loaded therein.
The distinguishing holes for distinguishing the novel magnetic disc cartridge having a larger storage capacity should be provided not to interfere with the medium sensor. Otherwise malfunction of the disc drive system can be caused.